Commercial

Servicing and Emptying

With 50 years experience, you can be rest assured we can maintain your sewage treatment plant to the highest level. Our well stocked Vans allow us to deal with most problems on site withoug tht need for a return visit.

Knowledge Centre

HOW TO SIZE A SEPTIC TANK

Owls Hall Environmental How To Guide

A septic tank is used where no mains sewage connection is available, and the water can be discharged through the ground via a soakaway or drainage field. If you want to know how to size a septic tank, look no further.

Septic tanks are not allowed to discharge to a ditch. Upgrading from a septic tank to a sewage treatment plant will allow discharging to a ditch and provide cleaner water increasing the life of a soakaway should one be used. Learning how to size a Septic Tank is important to ensuring it conforms with building regulations and provides long term performance.

The below is a guide to sizing a septic tank, with worked examples for single and multiple properties.

Step 1 – Find out how many people the property can accommodate.

British water flows and loads 4 document states that:

A single property of up to 3 bedrooms must be sized at 5 people.

A single property of 4 bedrooms must be sized at 6 people.

A single property of 5 bedrooms must be sized at 7 people

A single property of 6 bedrooms must be sized at 8 people

Multiple properties are sized individually and then added together.

Example A:

4 bedrooms = 6 people

A reduction factor is used where populations exceed 12 people This is to account for the fact that it is highly unlikely each property will be full. From 13-25 population, you can reduce the figure by multiplying the population by 0.9. From 26-50 population, you can reduce the figure by multiplying by 0.8.

For sizing of a septic tank for a commercial building, more detailed calculations must be made to ensure the daily flow is accurate. This is done using the British water flows and loads 4 Document. For assistance with this, our technical team can help on 01844 202121.